The European X-ray Free Electron Laser (XFEL.EU) is an international research facility presently under construction in the area of Hamburg, Germany, which will start its operation at the end of 2016. The superconducting linear accelerator of the facility will deliver electron bunches with an energy of up to 17.5 GeV, arranged in trains of typically 2700 bunches at a repetition rate of 4.5 MHz. Each train will be followed by a gap of 99.4 ms. Spatially coherent X-rays are generated from the electron bunches in a series of undulators based on the Self-Amplified Spontaneous Emission (SASE) process, in three photon beamlines extending over a length of up to 200 m. Each beamline serves two experiments with different scientific goals.